Obesity – and the nation's expanding waistlines – are never far from the headlines.

And when it comes to cancer, weight is important: carrying excess weight is an established risk factor for the disease, and the growing size of the problem in the UK is something that we have blogged a lot about before.

In fact, after smoking, statistics show it's the second-most important lifestyle-related cause of cancer.

We already know that is linked to 9 types of cancer, some more convincingly than others.

But this week, new evidence from the World Cancer Research Fund – an organisation with substantial expertise in cancer prevention – has concluded that as well as these types, carrying extra weight can also cause .

And what makes this report so important is that it concluded that there is the same high level of evidence for the link between liver cancer and bodyweight as there is for well-established obesity-linked cancers like breast and bowel cancer.

But as well as this new evidence, in the last year research has established being overweight as a probable cause of ovarian and advanced prostate cancers.

It's clearly a big issue. So what can we do about it?

Health choices vs. government action?

While nothing can guarantee that someone won't develop cancer, leading a healthy lifestyle can stack the odds in your favour.

In fact, research has shown that more than 4 in 10 cancers are preventable through lifestyle changes – and as well as keeping a healthy weight, these include being a non-smoker, eating a healthy diet, drinking less alcohol, being safe in the sun and being physically active.

We know it can be hard to lose weight if you are overweight. But ultimately making lasting changes to your lifestyle is the most effective way to maintain a healthy weight.

But while making healthy choices as individuals is crucial to reducing the number of people who are overweight or obese in the UK, we can't just rely on individual action to bring about positive change.

And that's where comes in. It can play a big role in helping us to maintain a healthy weight, by making evidence-based changes to help make sure that keeping a healthy weight becomes the norm once again.

MPs agree: obesity matters

In another announcement you may have missed this week, the government's Health Select Committee – an influential group of MPs who oversee the government's health policies – published their recommendations about the impact of diet and exercise on health.

Among a range of recommendations, they've emphasised the importance of physical activity in improving our health, and the benefits of preventing obesity at an early stage, before reaching the need for avoidable weight-loss surgery. We submitted evidence to the Committee last year, and we're delighted to see they support the need for more preventative action.

We know there are no quick fixes when it comes to tackling obesity. But there is growing evidence about what works. A recent report from management consultants McKinsey highlighted that Governments should not seek the single 'best' intervention but aim 'to do as much as possible, as soon as possible.'

Reviewing 44 different possible policies, the report found that all of them were cost-effective in reducing obesity, and that implementing all of them together could reduce the number of people who are overweight or obese by a fifth, saving the NHS over £800m a year.

44 interventions might sound like a daunting list to any government, so here are the three things we think are most important:

1. Helping people to stay active in their communities

An important part of tackling obesity, as well staying healthy in general, is to help people stay active.

At a local level, the Government can make it easier for people to build physical activity into their daily lives.

This means investing in sports facilities, open space, and environments where we can 'travel actively' – for example, by walking or cycling – which will help more people to meet the Chief Medical Officer's recommended guidelines for physical activity.

It will also help these options become a more central part of our commutes, neighbourhoods and playgrounds.

Local authorities should create supportive environments which promote physical activity

2. Cut consumption of high-sugar drinks

Another opportunity for action is tackling the affordability of .

As a nation, we drink more than 5.6 million litres of sugary drinks every year. The World Health Organisation has recently advised that sugars should make up less than 10 per cent of our calorie intake, though many have far more sugar in their diet than this, and sugary drinks are young people's biggest source of sugar.

What's more, they offer little to no nutritional value, and are associated with weight gain.

Evidence suggests that a 20 per cent tax on sugary drinks would reduce the number of people who are overweight by about 285,000 in the UK, with the biggest benefit for young people.

We believe that government should follow the lead of other countries such as France, Mexico and Hungary and look at this measure in the UK.

Cutting how many fizzy drinks we consume could help to reduce weight levels in the UK

3. Better food labelling

We've had real success working with Government and others on 'front of pack' food labelling, empowering people to make healthier choices about their diet.

This colour coding helps to inform people about the levels of sugar, salt, fat and calories, helps them to identify healthier alternatives, and gives manufacturers extra encouragement to turn red labels into green ones.

We'd like to see as many products as possible use traffic light labelling to help people identify healthier options across a wider range of products.

We need a full basket… of policies

With obesity being an issue of growing importance for cancer risk, it is important to address it by empowering people to maintain a .

This report from the WCRF has highlighted a few measures that can help, but – most important of all – we want the Government to draw up a new, comprehensive strategy, that includes a range of evidence-based measures to increase and improve diets.

We stand the best chance of reducing our cancer risk by moving away from piecemeal action, towards a coherent approach. With the evidence growing about obesity and , and more MPs calling for increased efforts to tackle obesity, pressure is mounting for the Government to take leadership to tackle this issue.

There's not a moment to lose.

More information: "Overall and income specific effect on prevalence of overweight and obesity of 20% sugar sweetened drink tax in UK: econometric and comparative risk assessment modelling study." BMJ 2013; 347 doi: dx.doi.org/10.1136/bmj.f6189

Journal information: British Medical Journal (BMJ)

Provided by Cancer Research UK